The present invention relates to a non-polluting oxyhydrochlorination process. More particularly, it relates to a process of oxyhydrochlorination by which the residual gaseous effluents are purified by catalytic oxidation and washing before discharge into the atmosphere.
The conventional methods for producing chlorinated derivatives of ethylene and, in particular, 1,2-dichloroethane, by oxyhydrochlorination do not provide 100 percent selectivity. Thus, the effluent emerging from the oxyhydrochlorination reactor always contains larger or smaller amounts of by-products. These by-products are complex mixtures which contain, in particular, in addition to unreacted hydrochloric acid and ethylene, carbon monoxide, carbon dioxide, and chlorinated organic compounds, such as ethyl chloride, 1,1-dichloroethane, the trichloroethanes, the tetrachloroethanes, the dichloroethylenes, trichloroethylene, chloroform, carbon tetrachloride, chloral, perchlorethylene, etc.
The removal of the chlorinated derivatives of ethylene from the effluent emerging from the oxyhydrochlorination reactor, never having in practice been quantitative, the residual effluent which results therefrom contains nitrogen, oxygen, as well as variable amounts of the chloro derivatives of ethylene which are sought, such as 1,2-dichloroethane, and variable amounts of the by-products mentioned above.
In order to treat such effluents, it has already been proposed, in accordance with French patent application No. 2,279,703, to pass them, at a temperature of between 300.degree. and 450.degree. C., over a catalyst bed, formed of a support of alumina or silica, on which 10 to 50% by weight of chromium oxide has been deposited. However, such a process has the drawback, in particular, that it is not selective and of favoring the Deacon reaction of formation of molecular chlorine from hydrochloric acid and oxygen. This formation of molecular chlorine, differing from hydrochloric acid, is extremely disturbing since it is difficult to eliminate from the gaseous effluents by conventional techniques, such as scrubbing with water. Furthermore, the presence of molecular chlorine in the presence of water vapor may lead to problems of material corrosion which are particularly disturbing at high temperatures. Finally, the catalysts having a base of chromium oxide are of only indifferent effectiveness for the oxidation of carbon monoxide to carbon dioxide.
By means of the present invention a process is provided which makes it possible to obviate these drawbacks and which uses a catalyst which is active, stable, and very selective for the oxidation of the carbon monoxide and hydrocarbons, wether or not chlorinated.
It is, accordingly, an object of the present invention to provide a novel non-polluting process for oxyhydrochlorinating, particularly for oxyhydrochlorinating ethylene, which is free from the disadvantages of the prior art.
It is another object of the invention to provide a non-polluting selective process for the oxidation of carbon monoxide and chlorinated and non-chlorinated hydrocarbons.
It is a further object of the invention to provide catalyst compositions having great utility in treating chlorinated organic compositions containing up to 10 carbon atoms.
Other objects of the invention will be apparent to those skilled in the art from the present description.